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81.
The anaerobic oxidation of methane (AOM) with sulphate, an area currently generating great interest in microbiology, is accomplished by consortia of methanotrophic archaea (ANME) and sulphate-reducing bacteria. The enzyme activating methane in methanotrophic archaea has tentatively been identified as a homologue of methyl-coenzyme M reductase (MCR) that catalyses the methane-forming step in methanogenic archaea. Here we report an X-ray structure of the 280?kDa heterohexameric ANME-1 MCR complex. It was crystallized uniquely from a protein ensemble purified from consortia of microorganisms collected with a submersible from a Black Sea mat catalysing AOM with sulphate. Crystals grown from the heterogeneous sample diffract to 2.1?? resolution and consist of a single ANME-1 MCR population, demonstrating the strong selective power of crystallization. The structure revealed ANME-1 MCR in complex with coenzyme M and coenzyme B, indicating the same substrates for MCR from methanotrophic and methanogenic archaea. Differences between the highly similar structures of ANME-1 MCR and methanogenic MCR include a F(430) modification, a cysteine-rich patch and an altered post-translational amino acid modification pattern, which may tune the enzymes for their functions in different biological contexts. 相似文献
82.
A map of the cis-regulatory sequences in the mouse genome 总被引:1,自引:0,他引:1
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Summary The local anesthetic effects of cocaine and one of its main metabolites norcocaine, were investigated comparatively on isolated ganglion cells of the marine gastropod,Aplysia californica. During a 1-hour-period, different action potential parameters such as amplitude, duration, maximum rate of rise were observed, which demonstrated that norcocaine exhibits a higher local anesthetic potency than cocaine.Acknowledgments. The authors are grateful to Dr M. R. Klee and Dr M. R. Park for helpful discussion. The work was partly supported by Österreichischer Fonds zur Förderung der wissenschaftlichen Forschung 相似文献
85.
Ulrich Hoyer 《Archive for History of Exact Sciences》1974,13(4):359-375
Ohne Zusammenfassung
Vorgelegt von
M. Klein 相似文献
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88.
Distinct t(7;9)(q34;q32) breakpoints in healthy individuals and individuals with T-ALL 总被引:3,自引:0,他引:3
After V(D)J-mediated translocations, signal joints are retained on one of the derivative chromosomes. We report here that such signal joints are highly reactive and constitute unstable genomic elements with potential oncogenic properties. 相似文献
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90.
Gleyzes S Kuhr S Guerlin C Bernu J Deléglise S Busk Hoff U Brune M Raimond JM Haroche S 《Nature》2007,446(7133):297-300
A microscopic quantum system under continuous observation exhibits at random times sudden jumps between its states. The detection of this quantum feature requires a quantum non-demolition (QND) measurement repeated many times during the system's evolution. Whereas quantum jumps of trapped massive particles (electrons, ions or molecules) have been observed, this has proved more challenging for light quanta. Standard photodetectors absorb light and are thus unable to detect the same photon twice. It is therefore necessary to use a transparent counter that can 'see' photons without destroying them. Moreover, the light needs to be stored for durations much longer than the QND detection time. Here we report an experiment in which we fulfil these challenging conditions and observe quantum jumps in the photon number. Microwave photons are stored in a superconducting cavity for times up to half a second, and are repeatedly probed by a stream of non-absorbing atoms. An atom interferometer measures the atomic dipole phase shift induced by the non-resonant cavity field, so that the final atom state reveals directly the presence of a single photon in the cavity. Sequences of hundreds of atoms, highly correlated in the same state, are interrupted by sudden state switchings. These telegraphic signals record the birth, life and death of individual photons. Applying a similar QND procedure to mesoscopic fields with tens of photons should open new perspectives for the exploration of the quantum-to-classical boundary. 相似文献